all true protonephridial types including terminal flame 

 cells. In all these groups the system opens posteriorly 

 through either a single orifice, paired separate 

 orifices, or in a cloaca. The nemic tubular 

 system presents a very striking resemblance to 

 the protonephridial system but despite conscientious ef- 

 forts terminal flame cells have not been demonstrated. 

 The canalicular H-shaped system could be homologized 

 (barring flame cells) with the rotatorian system if we 

 conceive of a new terminal duct connecting with the 

 anterior junction (Huxley's anastomosis) of the lateral 

 canals of Monogonontea rotatorians (see Remane, 1929). 

 The auxiliary excretory system of certain female rhab- 

 ditids has a striking superficial resemblance to the 

 paired system of gastrotrichs. 



The amphids of nemas seem to check well with the 

 retrocerebral organs of rotatorians and the lateral or- 

 gans of gastrotrichs, rhabdoco«le turbellarians and trem- 

 atode larvae. Paired lateral or sublateral glands or 

 glandular setae have their counterparts in the adhesive 

 gland tubes of gastrotrichs, the deirids (cervical papillae) 

 have been compared with the lateral antennae of rotator- 

 ians, while the phasmids may be compared with the 

 caudal antennae (Kaudaltaster) of monogonontic rota- 

 torians, and the caudal glands and spinerette with the 

 paired caudal toes of both rotatorians and gastrotrichs. 

 The existence of three caudal glands and a single spiner- 

 ette is not especially objectionable in such a comparison 

 since each of the two toes of gastrotrichs may be provided 

 with three such glands. 



The somatic musculature, triradiate esophagus, cuticle, 

 and lack of parenchyma all seem to argue for closest 

 relationship of nemas with the rotatorian series. The 

 non-symmetric pharynx of platyhelminths (Turbellarea 

 and Trematodea) while undoubtedly homologous to the 

 triradiate pharynx (nemic esophagus) of the rotatorian 

 series, must be considered as indicative of a separate 

 phylogenetic branch. The reproductive system gives no 

 help nor does it indicate any other possible relationship. 

 In the Gastrotricha we do find separate openings in both 

 systems (hermaphrodites) ; usually they are posterior 

 but occasionally they are anterior and the gonads are 

 always parallel. The opposed gonads must have been 

 coincident with elongation (hence origin) of nemas and 

 dependent on the essential nemic body form. 



Throughout this publication we have tended to question 

 total absence of cilia in nemas (so-called arthropod 

 character*), there being so many suspicious cases where 

 a ciliate structure seems clearly pre.sent but vibration 

 has not been observed. Contrast with arthropod and 

 annelid characteristics (lack of true metamerism and 

 of a true coelome, musculature, lack of arthropod chitin 

 in the adult exoskeleton, different symmetry etc.) seems 

 so obvious we feel no need for special discussion. One 

 point, the rectal glands of nemas and their comparison 

 with malpighian tubules, warrants thought, especially 

 when one considers multiplication of these glands (p. 115) 

 and the resultant similarity to those of tardigrades. If 

 there were anything to this we would have to hypothesize 

 arthropods as derived from primitive nemas via the 

 Tardigrada, which view would be objectionable to all 

 good entomologists. It is probably a matter of converg- 

 ence. Oddly enough, the only other counterpart for the 

 rectal glands is in the anal glands of gastrotrichs. 



Determinate bilateral rather than radial cleavage sets 

 the Rotatoria, Gastrotricha, Echinodera, Nemata and, 

 according to some authors, the Acanthocephala (Nema- 



•Dr. H. J. Van Cleave states Foster reported cilia trom the 

 gonoducts ot crabs. 



tomorpha not investigated) apart from platyhelminths, 

 annelids, and arthropods. Absence of nurse cells in the 

 egg, triradiate esophagus (when present) and external 

 cuticle provide further differentiating characters separ- 

 ating the first five groups from the Platyhelmintha. 

 Musculature does not provide a clear basis of separation, 

 nor does parenchyma (see Gordius vs. Nectonema within 

 Nematomorpha). However, pending further evidence we 

 will conclude this discussion by accepting the Aschelmin- 

 tha concept (Rotatoria-Gastrotricha-Echinodera-Nemata- 

 Acanthocephala-Nematomorpha) t and placing it in a 

 superior group Protonephridia which would also include 

 the Platyhelmintha (Turbellarea-Trematodea-Cestodea) 

 and the Nemerta. 



Tabular Comparison of Groups 



Purely for supplementary consideration a table is 

 given in which there are brief characterizations of the 

 various organs of some of the invertebrates (Table 4). 

 The writer has used this table in teaching and found it of 

 some value. A conscientious attempt was made to at- 

 tain accuracy but doubtless there are many errors. 



Based on the anatomical characters given in table 4, 

 a system was devised whereby the degree of similarity 

 of each group with every other group could be expressed 

 numerically. Each anatomical category was assigned a 

 value of 6. Thus in table 5 the Trematodea are compared 

 with the other groups in respect to each of the 16 

 anatomical characters given in table 4. Recorded in 

 column 1 of table 5 are scores based on a comparison of 

 the exoskeleton. When the exoskeleton of the Trematodea 

 was compared with that of the Nemata a score of 

 was given, indicating no similarity; when compared to 

 the Rotatoria a score of 4 was given, indicating a certain 

 degree of similarity, etc. In the next vertical column 

 (2) scores are recorded based on the ectodermal ei^ithel- 

 ium, in the third vertical column (3) scoiies based on 

 the somatic musculature, etc. The scores are totaled in 

 the right hand vertical column. In this table, it will be 

 noted, the Trematodea are compared with the Trematodea, 

 resulting in a total score of 96 which is, of course, the 

 highest possible score. In the following discussion the 

 score of a given group when compared with itself will 

 be referred to as the base score. 



A similar table was prepared for each of the 12 

 other invertebrate groups under consideration. These 

 tables are not reproduced herein but the totals, i. e., 

 the scores in the right hand vertical column of each are 

 assembled in table 6. Thus in vertical column "N" of 

 table 6 are recorded the scores resulting from a compar- 

 ison of the Nemata with the other groups. In the fol- 

 lowing discussion these scores will be referred to as the 

 Nemata> score series, those in the next vertical column as 

 the Rotatorian score series, etc. When information re- 

 garding one or more anatomical feature was lacking 

 the base score is less than 96, as for example, the base 

 score for the Echinodera, Rotatoria and Acanthocephala 

 is, in each case, 90, and for the Gastrotricha, 84. 



Whether or not this system is valid, it gives an in- 

 teresting numerical comparison of apparent similarities. 

 By using- all organs the stress of possible convergent 

 characters is lowered. We regard the relative as well 

 as the actual scores as having significance. In each 



fin the following discussion (Tabular comparison of groups) 

 it will be seen that an evaluation of morphological similarities 

 removes the Acanthocephala to the Platyhelmintha. 



Fig. 14.'>. RELATIVES OF NEMATODES 



A — Cyclorhagae (Echinodera), ventral view. B — Chaetonotus 

 (Gastrotricha). ventral view. C — Tarbanella rornutn (Gastrotricha), 

 ventral view. D — Gordiits aquatlcus (Nematomorpha). lateral view 

 of larva. EG — Monogononta (Rotatoria) (E — Dorsal 

 view; F — Ventral view; G — Lateral view). H — Zelinkiella 

 synaptae (Rotatoria), nervous system. I-K — Pycnophes communis 

 (Echinodera) (I — Excretory system; J — Cross section in pharyn- 

 geal region ; K — Horizontal section of pharyngeal region). L-M — 

 Cha^Jovotus mcirhnui (Cross sections. L-— At level of pharynx; M — 

 At level of intestine). M — Macrorlnsys (Gastrotricha) (Adhesive 

 tube setae of v.irious types). 0-P — Turbaiirlla for:>utn (Cross 

 section. O — At level of pharynx; P — At level of intestine). Q-T- — 

 Gordius aqtwlhus larva (Q — En face view ; R-T — Proboscis region 

 in various stages of contraction). U — GoriVnis larva (Cross section 

 near base of proboscis). V-W — Gordius adult (V — Cross section of 

 ventral chord showing ganglion cell groups ; W — Diagram of 

 nervons system). X-DD — Diagrams of female reproductive system 

 of nomas (DD — Hypothetical form). EE-HH — Comparison ot 



nemas and rotifers (EE-FF — without caudal glands; GG-HH — with 

 caudal glands). II — Gordius tolosanns (Cross section of female) 

 JJ-LIj — Nri-foiidiia agile (Nematomorpha) (JJ — Ci'oss section of 

 male; KK — Cross section of female LL — Muscles and oocyte). 

 M.M-NN — .Macrobiotus hufelandi (Tardigrada) (MM — Female; NN — 

 Ci-oss section of pharynx). 00 — Diagram of nervous system in 

 Acanthocephala. A & IK. after Remane. 192S, Die Tierwelt der 

 Xord-u. Ostsee, Part 7d 2 ; B 6 LP after Remane 1029, Handb. 

 Zool. V. 2 (6) ; D & Q-T after Dorier, 19.30. Recherches biologiques 

 ft systematiques sur les Gordiaces. Thesis Grenoble ; E-G, after 

 Remane. 1929. Die Tierwelt dor Nord-u. Ostsce part 7 e ; tJ, 

 after Rchepoticff. 190S. Ztschr. Wiss. Zool. v. <S9 ; V-W & 00, after 

 Brandes, 1899, Abhandl. Naturf. Gesellsch. Halle, v. 21 ; X-DD, 

 After Steiner, 1919, Untersuehungen ueber den allgemeinen Bauplan 

 des Nematodenkoerpers. Jena ; EE-HH after Steiner 1919, Fest- 

 schrift f. Zschokkc (31) ; II. after Rauther 1905, Jena Ztschr. 

 V, 40, n. t. V, :',:) (1) ; JJ-LL after Fcyel, 1936, Arch. Anat. 

 Microsc. V. 32; MM-NN after Cuenot, 1932. Faune de Prance (24). 



197 



